Don't judge strangers by pre-conceived ideas.

pre-conceived 是由前缀 pre-（表示“在...之前”）和动词 conceive（构想、设想）的过去分词 conceived 组合而成。conceive 本意是"构思、设想"。 pre-conceived 字面意思是"事先构想好的"，引申为"先入为主的、预先形成的"。